Probiotic Found to Slow Disease Spread Among Florida Coral

A beneficial bacterial probiotic is restoring hope for mitigating disease spread in corals off the coast of Florida. In a new study, scientists have investigated the effectiveness of a compound produced by the probiotic strain MCH1-7 for combating the deadly stony coral tissue loss disease.

MCH1-7 was first uncovered by scientists from the Smithsonian Marine Station in 2018 and was found on a coral colony that had naturally resisted an outbreak of stony coral tissue loss disease (SCTLD).

Scientists have previously tested the bacterial probiotic on adult corals, but now have published research in the journal Frontiers in Marine Science on how this probiotic could limit disease spread in young corals. Scientists are investigating a compound known as tetrabromopyrrole (TPB), which is produced by the bacteria, and how it may protect entire colonies from the disease.

“If TBP is a natural settlement cue, and if bacteria that also produce this compound protect corals from disease, it makes sense that larvae would settle where those compounds are being produced,” Jennifer Sneed, biologist at Smithsonian Marine Station, said in a statement. “More of them would survive to be able to recognize the compound.”

To test the compound, researchers applied the probiotic to great star coral (Montastraea cavernosa) in two different ways: injecting the probiotic into seawater inside a weighted bag placed around the coral, and through a paste applied directly to disease-related lesions on the coral. The former method allowed observers to test for whole-colony treatment effectiveness. From there, the team monitored the corals and tested coral samples for 2.5 years after treatment.

As Mongabay News reported, the corals treated via whole-colony treatment lost about 7% of tissue from the disease, compared to untreated corals that lost 35% of their tissue on average to SCTLD. These results continued over the course of the research, with the probiotic treatment slowing the disease spread for 2.5 years after application.

However, the paste application to individual lesions was not similarly effective. 

In response, the researchers determined a way to apply the probiotics to corals via scuba diving and confirmed the method would not disrupt other healthy Caribbean coral species, which could lead to a useful SCTLD treatment for full coral colonies in the future.

“While the whole-colony bagging method does involve more material transport by divers and more time for deployment and retrieval, its performance at treating SCTLD and promoting long-term resistance outweigh these costs and is therefore the recommended application method of those we tested for probiotic treatments such as the McH1–7 strain,” the authors wrote in the study.

The authors stressed that more research is needed to make this potential treatment a reality, and additional studies should be done to uncover further treatments for treating various coral species affected by the deadly stony coral tissue loss disease.

“It’s important to understand that this is the very beginning,” Kelly Pitts, lead author of the study and researcher at Smithsonian Marine Station, told Mongabay News. “This is definitely not a cure-all, but we’re definitely moving in the right direction.”